Abrasive wheel structure



Aug. 6, 1957 Filed Jan. 24. 1956 J. R. M m'rosH ETAL 2,801,504

ABRASIVE WHEEL STRUCTURE 2 Sheets-Sheet l INVENTORS:

ATTORNEYS.

. Aug. 6, 1957 J MaclNTQSl-l ET AL 2,801,504 I ABRASIVE WHEEL STRUCTURE 2 Sheet-$heet 2 g I ATTORNEYS.

assrsai Patented Aug. 6, 1957 United States Patent Ofiice 2,801,504 AsRAsivE WHEEL STRUCTURE John R. M acl ntosh and Sam A. Mercurio, Chicago, Ill., assignors to Mermac Products, Inc., Chicago, Ill, a corporation of Illinois Application January 24, 1256, Serial No. 560,931

16 Claims. (Cl. 51 -191) This invention relates to an abrasive wheel structure, and more particularly to a structure having an endless abrasive bel-t removably carried by a support wheel or disc. The structure is useful in the grinding or abrading of articlesfor example, wood, metal or plastic, depending upon the character of the abrasive belt--and may be employed in conventional manners as part of a portable or fixed unit.

In abrasive wheel assemblies wherein an endless abrasive belt is supported upon a wheel or disc, it is necessary to replace the belts from time to time as they become worn through use, and in the event it may be desirable to change the belts in order to select the abrasive characteristics thereof for rough grinding and polish finishing, or to provide belts having abrasive characteristics particularly suited for a given material upon which grinding operations are to be performed. Therefore, an assembly that provides ready removability and replacement of abrasive belts is desirable, and it is accordingly an object of this invention to provide such an assembly.

When an assembly of this character is in use, it is a requisite that the endless belt be firmly gripped by the wheel or disc so that there will be no slippage therebetween. As a result, it is another object of this invention to provide an assembly having this desirable characteristicas well as one that provides ready removability. and

replacement of the abrasive belts.

Still another object of the invention is in the provision of a support wheel or disc useful in an abrasive wheel structure; and wherein the outer diameter of the wheel, when the wheel is stationary, is slightly less than the inner diameter of an endless belt to be used therewith; and that assumes a diameter equal to that of the abrasive belt when the wheel is rotating at operational speeds whereby, when the wheel is stopped, abrasive belts may be removed and replaced with ease, and when the wheel" is in motion, it tightly grips the belt .to prevent slippage thereof.

'Afurther object of the invention is. that of providing a support wheel for an endless abrasive belt that is characterized 'by havinga 'given outer diameter when the wheel-j is stationary, and that has an enlargeddiameter when the wheel is rotated, which is brought about by the centrifugal forces acting along the radii of the wheel,

. side view in elevation of the same structure, but showingithe, opposite side. thereof; Figure 3 is a vertical sectional yiew taken along the line 33 ofFigure 1; Figure 4 is a; broken angular sectional view takenalong the line 4 -4 of Figure 2; Figure. 5 is a side" view in elevation of a modified form of abrasive wheel; Figure 6 is a side view in elevation of the same wheel showing the opposite side thereof; and Figure 7 is a transverse sectional view taken along the line 77 of Figure 5.

The abrasive wheel assembly is designated with the numeral 10, and comprises a support wheel or disc 11 and an endless abrasive belt 12 that encircles the wheel, The endless abrasive belt may be of conventional construction and design insofar as the instant invention is concerned, and (as is customary) will have a backing, the outer surface of which is engrained with abrasive particles. Belts of this character being known in the art, it is believed unnecessary to set forth a further description thereof.

The wheel or disc 11 comprises an inner hub 13 that is substantially rigid and is preferably formed of aluminum. The hub 13 has an enlarged central recess 14 on one side thereof that serves to reduce its weight, and that defines the interior of an annular flange 15 along one side of the disc. The web of the hub has a central opening 16 formed therein that is adapted to receive a spindle or shaft that is rotatably driven. Appropriate means (not shown) will be provided for locking the disc upon the shaft so that it will rotate therewith.

The hub 13 is provided with a plurality of spaced apart channels 17 that extend circumferentially thereabout and that define ribs 18 therebetween. This is best seen in Figure 3 of the drawing. The hub is also provided with a plurality of circumferentially spaced apart recesses 19 that extend transversely across the circumferential surface thereof, and that define ears or lugs 20 therebetween. is best seen in Figures 1 and 2.

Mounted upon the hub 13 is a disc 21 that is formed of a resilient material, and it has been found that rubber provides an advantageous material from which the disc may be formed. Centrally, the disc 21 is provided with an enlarged opening 22 therethrough. The opening 22 is annular and is provided with a plurality of spaced apart channels 23 that extend circumferentially thereabout and that define ribs 24 therebetween. Extending transversely across the circumferential surface of the opening 22 are a plurality of circumferentially spaced apart recesses 25 that define ears or lugs 26 therebetween. The channels 17, ribs 18, recesses 19 and ears 20 (all of the hub 13) are adapted to mate with the complenientary or corresponding channels 23, ribs 24, recesses 25 and ears 26 (all of the disc 21) to form an interlock between these two components so that relative rotational movement therebetween is inhibited.

Preferably, the contiguous surfaces of the hub 13 and disc 21 are adhesively bonded together by any of the Well known adhesives that will provide a bond between metal (particularly aluminum) and a non-metallic material, rubber in the specific illustration given.

The disc 21 is provided with a row (designated generally with the numeral 27) of openings or passages 28a and 28b that extend transversely of the disc and have their centers aligned on a circular arc, the origin of which is the rotational axis of the wheel. That is to say, the outer row 27 is concentric with the circumferential surface of the disc 21, and lies a spaced distance inwardly therefrom. The passages 28a and 28b which comprise the outer row 27 are alternately staggered, all of the passages 28a opening outwardly on one side of the disc, while the passages 28b open outwardly on the other side of the disc.

The disc 21 is provided with a second or inner row 29 of spaced apart passages 313a and 39b. The passages 30a and 30b are parallel to the passages 28a and 28b,

and the row 29 formed thereby is concentric with the row 27, and in turn with the circumferential surface of This latter configuration of the hub the disc 21. The passages 30a and 30b open, respectively, onto opposite sides of the disc. It will be apparent from Figure 3 that the passages 28a and 30a open onto the same sideof the. disc, and similarly, the passages 28b and 3% open onto the opposite side of the disc.

The passages in the rows 27 and 29 are'staggered with respect to each other and are arranged in pairs the passages 28a and 30:: adjacent each other defining certain of the pairs, while the passages 28b and 30b which are adjacent each other define other of the pairs. It is apparent that the pairs of passages alternately open onto oppositesides of the disc 21.

The adjacent passages which define one of the many pairs of passages are connected together by slots or slitted portions of the disc 21. For purposes of identification,the slitted portions of the disc are designated with the numerals 31a and 31b, and these slitted portions interconnect, respectively, the paired passages 23a and 30a, and 28b and 3%. In the illustration given, there are thirty-two passages in each of the rows 27 and 29 and, therefore, thirty-two paired passages-the passages of each pair communicatin with each other through the slitted portions of the disc.

The wheel structure 11 may be fabricated in two parts, as has been brought out hereinbefore, and the parts or components thereof-namely, the hub 13 and disc 21- can then be assembled by stretching the disc over the hub and positioning it so that the interlocking recesses, ears, channels and ribs of each component mate. Thus, the disc is fixedly anchored to the hub 13 and if an adhesive bond between these two components is employed, a fur ther fixing of each to the other is brought about.

\Vhen the wheel structure is stationary, an abrasive belt 12 can easily be positioned thereon, for the outer diameter of the disc 21 will be slightly less than the inner diameter of the endless belt. Therefore, replacement and interchanging of belts 12 is achieved with case. On the other hand, when the wheel structure is rotated, the disc 21' assumes an enlarged diameter which is effective to provide a tight frictional grip between the circumferential surface thereof and the inner surface of the endless abrasive belt mounted thereon. The frictional gripbecomes progressively greater as the rotational velocity of the wheel increases, for the increase in diameter of the disc is effectuated by centrifugal force. As is well known, the centrifugal force increases with velocity, whereby there is an incremental progression in the expansion of the disc that is directly proportional to the rotational velocity thereof.

The wheel structure can be rotated at a relatively high velocity without requiring a large power source, for the weight of the wheel is substantially decreased by providing a cavity or chamber 14 in the hub thereof, and by providing the passages 28 and 3th in the disc thereof. The slitted areas 31a and 31]) that connect the paired passages in the outer and inner rows 27 and 29 form weakened portions in the disc 21, or portions whereat the inherent resistance to deformation is decreased, with the result that centrifugal forces acting radially of the disc are more effective toincrease the outer diameter thereof when the disc is rotated.

It is important that each increment of the disc 21 along the circumferential surface thereof expands to the same extent when the wheel is rotated, or else irregularities would be provided in the abrasive surface of the endless belt 12. The slits 31a and 31b extend angularly with respect to the radii of the disc, since they interconnect passages in the inner and outer rows, and those passages are oifset angularly or arcuately with respect to each other.

It will be noted particularly in Figures 1 and 2, that the adjacent slits 31a and 31b form a continuous slitted area extending about the disc 21. This is apparent if a line is drawn between the inner passage of one pair and the outer passage of the adjacent pair, and it is considered that the passages provide extensions of the slitted areas. Referring to Figure 3, it is noted that the passages 28a and 30a extend inwardly from one side of the disc to a distance about three-fourths the width of the disc. Similarly, the passages 28b and 30b extend inwardly for approximately the same distance from the opposite side of the disc. Thus, the center portion of the circumferential surface of the disc for an area equal to about one-half the width of the disc overlies the slits 31a and 311'). Thus, any point taken along the circumerential surface of the disc within this area overlies a slitted portion of the disc.

When the disc is rotating at high speeds, there is a seemingly greater tendency for the central one-half portion of the disc to assume a greater diameter than the edge portions thereof because of the continuity between the slits 31a and 31b that underlie this area. However, there is normally a greater tendency for the edge portions of the disc to be'thrown outwardly agreater amount than the center (in the absence of the slits) because of the lesser quantity of material at such points that is, the edge portions are free along their outer sides. Therefore, the center slitted arrangement provides a release at the center of the disc, while the edge portions are notreleased with the result that the disc, in expanded condition, provides a uniform or smooth surface.

The modified form of structure shown in the drawings is essentially the same as the heretofore described, and differs therefrom only in the manner in which the rubber disc is secured to the inner hub; It will be apparent also that the hub itself differs somewhat from that illustrated in connection with Figures 1 through 4, and which has already been described in detail. The modified wheel structure is particularly suited where large diameter wheels are required. For example, it is particularly suited for wheels having diameters up to and in excess of 16". On the other hand, the abrasive wheel shown in Figures 1 through 4 is more suited for use where the diameter is relatively small as, for example, about 6".

In this form of the invention, the rubber disc is des ignated with the numeral 36 and has an outer row of spaced apart passages 37 formed of passages 38a and 38b that enter the disc from opposite sides thereof. The disc also has an inner row of passages 39 formed of spaced apart passages 40a and 40b. Slits 41a and 41b connect the respective passages in the inner and outer rows 37 and 39. With respect to the spaced apart rows of apertures and the slitted portions that interconnect the same, the wheel 36 is identical with the wheel 10 heretofore described, and no further description of this portion of the wheel will be set forth herein.

The disc 36 has an enlarged central opening 42 therethrough, and an annular recess 43 opening into the open central area 42 at substantially the mid-point thereof. Received within the annular recess or channel 43 is a hub or support plate 44 that has reinforcing flanges 45 and 46 on each side thereof, but of diameters such that they terminate spaced distances from the disc 36. The support flanges 45 and 46 may be rigidly secured to the plate 44 in any suitable manner, such as by welding. The plate 44, as well as the support flanges abutting each side thereof, are formed with a central bore 47 there through adapted to receive the spindle of a motor or other drive member by means of which the wheel can be rotated.

The disc 36 is further secured to the plate 44 by means of a plurality of pins arranged in two rows 48 and 49, those in the outer'row being designated with the numeral 50a while those in the inner row are designated with the numeral 50b. The outer row 48 has a plurality of spaced apart pins 50a concentric about the rotational axis of the wheel, and similarly, the inner row 49' has a plurality of spaced apart pins'50b that are concentric about the rotational' axis of the wheel. As is best seen in the side view, the pins of the inner and outer rows are staggered or are offset with respect to' each other.

The pins are received within openings provided for that purpose in the plate 44, and preferably are secured in fixed relation with respect thereto through the medium of a press fit. It will be apparent thatthe rubber disc 36 is provided with passageways extending completely therethrough for receiving the pins therein. For pur- .poses of numerical designation, the passageways through the rubber disc are designated with thenumeral 51. All

of the pins are effective to prevent the disc 36'fromi rotating with respect to the plate 44, andare further effective to prevent the disc 36 from being thrown outwardly or moved outwardly through the inner portion thereof by the centrifugal forces that develop upon rotation of the wheel.

In either form of the invention, the wheels function the same upon rotation thereof. The rubber discs are anchored to the hubs so that relative rotation therebetween is prevented, and at the same time the discs are secured to the hubs either by adhesives or by the pins 50a and 50b in the case of the modification, so as to obviate the possibility of the rubber discs being thrown or expanded by centrifugal force to the point where they become loose.

However, the rubber discs are permitted to expand under the influence of centrifugal force upon the rotation thereof so as to tightly grip an abrasive belt positioned thereabout. The grip, of course, becomes greater as the rotational velocity of the rubber discs increases. The discs provide a smooth outer surface gripping the abrasive belt because of the arrangement of the passageways that extend therethrough in the spaced rows along the circumferential surfaces thereof. That is, the passageways extend alternately from opposite sides of the disc and terminate at points about three-fourths of the width of the discs. The "central portion of the discs along the circumferential surfaces thereof overlie what are in effect substantially continuousslitted areas, whereby the central portions of the disc arereleased and are thereby permitted to expand outwardly when the discs are rotated. The edge portions of the discs, however, are not so underoutwith slitted portions and arenot so weakened orfreleased. The net result'is a uniform expansion of the discs throughout the entire peripheral surface area thereof, with the result that a belt carried thereby presents a uniform grinding or abrading surface.

While in the foregoing specification embodiments of the invention have been described in considerable detail for purposes of making a complete disclosure thereof, it will be apparent to those skilled in the art that numerous changes may be made in those details without departing from the spirit and scope of the invention.

We claim:

1. In an abrasive wheel structure adapted for use with an endless abrasive belt, a rigid hub adapted to be secured to a rotatably driven shaft, said hub having a plurality of channels extending circumferentially thereabout defining ribs therebetween and a plurality of circumferentially spaced recesses extending transversely thereacross and defining ears therebetween, a resilient disc having an enlarged central opening therethrough providing circumferentially extending channels defining ribs therebetween and transversely extending recesses defining ears therebetween, the channels, ribs, recesses and ears of the hub and disc being adapted to mate with each other to provide an interlock therebetween, said disc being resilient and having an inner and outer row of passages extending transversely thereof, said rows being concentric with the peripheral surface of said disc and alternate passages in each row extending partially across the disc and opening outwardly on opposite sides thereof, the passages of said rows being arranged in pairs and the passages of each pair being interconnected by slits, and an abrasive belt carried by said disc about the circumferential surface thereof, the outer diameter of said disc, when the disc is stationary, being less than the inner diameteryof said belt and when said disc is rotating at a velocity in excess of a predetermined value, said disc having antouter diameter equal to the inner diameter of said belt to frictionally lock the same in position thereon.

2. In a structure of the character described, a resilient disc adapted toreceive an endless abrasive belt about the circumferential surface thereof and being adapted to be rotated, said disc being provided with a plurality of offset passages extending transversely thereof and being characterized by enlarging to a greater diameter when rotated at an angular. velocity exceeding a predetermined value, said passages being oriented in an inner and'outer row both concentric withthe circumferential surface of said disc, alternate passages in each of said rows extending partially across said disc and opening outwardly therefrom on opposite sides thereof, said passages being arranged in pairs, one in each of said rows, and the passages in each pair being connected together by slitted portions of said disc.

3. In a rotatable expansible wheel structure of the character described, a resilient disc adapted to receive of the opposite side thereof to provide an overlapping relation with each other.

4. The structure of claim 3 in which. the correspondingpassages in adjacent rows and which extend inward ly from the same side of said disc are c onnected together by slitted portions of said disc.

5. The structure of claim 4 in which said correspond ing passages are offset arcuately from each other.

6 The structure of: claim 3 in which each of said assages extends from one side thereof inwardly into said disc for a distance of about three-fourths of thewidth -7.- The structure of claim 3 in which said plurality of rows comprises a pair, the passages in each row being substantially equally spaced apart and the passages of one row being offset arcuately from those: of the other row.

8. The structure of claim 7 wherein those passages of each row which extend inwardly from the same side of said disc are arranged in pairs, and in which said disc is slitted to interconnect each of said pairs.

9. In a Wheel structure of the character described, a substantially rigid hub adapted to be rotatably driven, a resilient disc adapted to receive an endless abrasive belt about the circumferential surface thereof, means for securing said disc to said hub to prevent relative rotational movement therebetween, said disc being provided with a plurality of offset passages extending transversely thereof and being characterized by enlarging to a greater diameter when rotated at an angular velocity exceeding a predetermined value, said passages being oriented in an inner and outer row both concentric with the circumferential surface of said disc, alternate passages in each of said rows extending partially across said disc and opening outwardly therefrom on opposite sides thereof, said passages being ararnged in pairs, one in each of said rows, and the passages in each pair being connected together by slitted portons of said disc.

10. The wheel structure of claim 9 in which said hub comprises an annular plate equipped With a plurality of pins extending transversely thereof and in spaced apart relation thereabout, each of said pins having portions thereof extending laterally of said plate on each side thereof, said disc having a width substantially as great as the length of said pins and said pins being embedded therein to provide the aforesaid means for securing said disc to said hub.

belt, means for securing said disc to said hub to pre-' vent relative rotational movement therebetween, said disc being provided with a plurality of concentric rows of circumferentially spaced passages extending transversely thereinto, thejalternate passages in each row extending inwardly from opposite sides of said disc and terminating interiorly thereof beyond the center of the disc but short of the opposite side thereof to provide an overlapping relation with each other.

12. The wheel structure of claim 11 in which said hub comprises an annular plate equipped with a plurality of pins extending transversely thereof an in spaced part relation thereabout, each of said pins having portions thereof extending laterally of said plate on each side thereof, said disc having a width substantially as great as the length of said pins and said pins being embedded therein to provide the aforesaid means for securing said disc to said hub.

13. In an abrasive wheel structure adapted for use with an endless abrasive belt, a relatively rigid hub, said hub comprising a circular plate adapted to be secured to a rotatably driven shaft and being equipped with a plurality of pins extending transversely therethrough at substantially equally spaced intervals along the circumferential surface thereof, said pins having projecting portions extending laterally of said plate on each side thereof, a resilient disc having a width substantially as great as the length of said-pins and having the pins embedded therein to anchor the disc to said hub, said disc having an inner and outer row of passages extending transversely thereof, said rows being concentric With the peripheral surface of said disc and alternate passages in each row extending partially across the disc and opening outwardly on opposite sides thereof, the outer diameter of said disc, whenthe disc is stationary, beingless than the inner diameter of such belt and when said disc is rotating at a velocity in excess of a predetermined value, said disc having an outer diameter equal to the inner diameter of suchbelt to frictionally lock the same in position thereon,

14. In a' rotatably expansible wheel structure of the character described, a'resilient disc adapted to receive a belt about the circumferential surface thereof and-to expand when rotated to grip such belt, saiddisc being provided with a concentric row of circumferentially spaced passages extending transversely thereto, the alternate passages in said row extending inwardly from opposite sides of said disc and terminating interiorly thereof beyond the center of the disc but short of the opposite side thereof to provide an overlapping relation with each other;

15. The wheel structure of claim 14 in which a hub' is provided, and in which means are also provided for securing said disc to said h-ub; said hub comprising an annular plate equipped with a plurality of pins extending transversely thereof and in spaced apart relation thereabout, each of said pins having portions thereof extending laterally of said plate on each side thereof, said disc having a width substantially as great as the length of said pins and said pins being embedded therein to provide the aforesaid means for securing said disc to said hub.

16. The wheel structure of claim 14 in which the circumferential surface of said disc is substantially continu ous and uninterrupted throughout the entire area thereof.

References Cited in the file of this patent UNITED STATES PATENTS 

